Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$108.57	7.408%	$116.6129	$116.61	$116.60	$116.60
Purchase #2	$239.84	6.801%	$256.1515	$256.15	$256.15	$256.20
Purchase #3	$73.98	9.190%	$80.7788	$80.78	$80.80	$80.80
Purchase #4	$89.58	13.744%	$101.8919	$101.89	$101.90	$101.90
Purchase #5	$38.27	4.711%	$40.0729	$40.07	$40.05	$40.10
Purchase #6	$235.59	8.228%	$254.9743	$254.97	$254.95	$255.00
Purchase #7	$59.35	8.540%	$64.4185	$64.42	$64.40	$64.40
7 purchase totals =	$845.18		$914.9008	$914.89	$914.85	$915.00